T8534: refactor sysctl_(read|write) to accept key parts

Interface names can contain dots (e.g. VLAN subinterfaces like eth0.10), which
conflicts with sysctl's dot-separated key syntax.

Change sysctl_read() and sysctl_write() to take key components as a list and
normalize each component by replacing . with / before invoking sysctl. This
fixes sysctl lookups/updates for VLAN subinterfaces.

Extend the SR-TE smoketest to cover a VLAN subinterface.

Previous error raising this issue:
  vyos-configd: sysctl: cannot stat /proc/sys/net/ipv6/conf/eth0/10/seg6_enabled: No such file or directory
  vyos-configd: sysctl: cannot stat /proc/sys/net/ipv6/conf/eth0/201/seg6_enabled: No such file or directory

1 files changed, 20 insertions, 14 deletions

diff --git a/python/vyos/utils/system.py b/python/vyos/utils/system.py
index 578537544..fd5f49645 100644
--- a/python/vyos/utils/system.py
+++ b/python/vyos/utils/system.py
@@ -16,28 +16,34 @@
 import os
 from subprocess import run
 
-def sysctl_read(name: str) -> str:
+def _sysctl_key(parts: list[str]) -> str:
+    normalized = (p.replace('.', '/') for p in parts)
+    return '.'.join(normalized)
+
+def sysctl_read(name: list[str]) -> str:
     """Read and return current value of sysctl() option
 
     Args:
-        name (str): sysctl key name
+        name (list[str]): sysctl key name components
 
     Returns:
         str: sysctl key value
     """
-    tmp = run(['sysctl', '-nb', name], capture_output=True)
-    return tmp.stdout.decode()
+    key = _sysctl_key(name)
+    tmp = run(['sysctl', '-nb', key], capture_output=True)
+    return tmp.stdout.decode().strip()
 
-def sysctl_write(name: str, value: str | int) -> bool:
+def sysctl_write(name: list[str], value: str | int) -> bool:
     """Change value via sysctl()
 
     Args:
-        name (str): sysctl key name
+        name (list[str]): sysctl key name components
         value (str | int): sysctl key value
 
     Returns:
         bool: True if changed, False otherwise
     """
+    key = _sysctl_key(name)
     # convert other types to string before comparison
     if not isinstance(value, str):
         value = str(value)
@@ -45,7 +51,7 @@ def sysctl_write(name: str, value: str | int) -> bool:
     if sysctl_read(name) == value:
         return True
     # return False if sysctl call failed
-    if run(['sysctl', '-wq', f'{name}={value}']).returncode != 0:
+    if run(['sysctl', '-wq', f'{key}={value}']).returncode != 0:
         return False
     # compare old and new values
     # sysctl may apply value, but its actual value will be
@@ -55,11 +61,11 @@ def sysctl_write(name: str, value: str | int) -> bool:
     # False in other cases
     return False
 
-def sysctl_apply(sysctl_dict: dict[str, str], revert: bool = True) -> bool:
+def sysctl_apply(sysctl_dict: dict[tuple[str, ...], str], revert: bool = True) -> bool:
     """Apply sysctl values.
 
     Args:
-        sysctl_dict (dict[str, str]): dictionary with sysctl keys with values
+        sysctl_dict (dict[tuple[str, ...], str]): dictionary with sysctl key components (tuple) with values
         revert (bool, optional): Revert to original values if new were not
         applied. Defaults to True.
 
@@ -67,12 +73,12 @@ def sysctl_apply(sysctl_dict: dict[str, str], revert: bool = True) -> bool:
         bool: True if all params configured properly, False in other cases
     """
     # get current values
-    sysctl_original: dict[str, str] = {}
-    for key_name in sysctl_dict.keys():
-        sysctl_original[key_name] = sysctl_read(key_name)
+    sysctl_original: dict[tuple[str, ...], str] = {}
+    for key_parts in sysctl_dict.keys():
+        sysctl_original[key_parts] = sysctl_read(list(key_parts))
     # apply new values and revert in case one of them was not applied
-    for key_name, value in sysctl_dict.items():
-        if not sysctl_write(key_name, value):
+    for key_parts, value in sysctl_dict.items():
+        if not sysctl_write(list(key_parts), value):
             if revert:
                 sysctl_apply(sysctl_original, revert=False)
             return False